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Hi all, I know that a lot of things are changing regarding the definition of products and properties, but I would like to know what is the current "standard" way to define custom properties for IFC building objects in an interoperable manner. I know it is possible to define custom properties at will in IFC files, but I'm looking for methods to document them properly. Is there a standard or bSI reference that indicates how this should be done? Should they follow the PSD-XML structure, e.g. as done for predefined properties and PSets: https://standards.buildingsmart.org/IFC/DEV/IFC4_2/FINAL/HTML/psd/? If yes, is there an XSD or any documentation of it?

Thank you for submitting your first issue. Community engagement is very important for us. Looking forward to further engagements.

yes, you can document it using the psd xml format. Alternatively you can use (since IFC4) also a subset of the IFC4 specification, namely the IfcPropertyTemplate and IfcPropertyTemplate to express the definition of a property set. See here for an example:

• https://standards.buildingsmart.org/IFC/RELEASE/IFC4/ADD2_TC1/HTML/link/listing-ifc4_add2.htm

the definition of the XSD for the property set XML format exists, it was part of the previous buildingsmart-tech.org site. @jwouellette - lets have a look if we can provide it again.

Thanks. I've had a hard time finding just the existing PSDs and could indeed not find the XSD! Would be good to have it on a stable location. Maybe the XSD and PSDs can also be provided in this Github repo?

I saw that this repo already has properties in XML format, but they seem to follow a different (non standard?) XML structure. What is the difference?

Is PSD in XML format actually defined in any of the ISO standards (e.g. ISO 16739-1:2018 or others)?

I believe PSD is a bespoke data serialization. They are also published in accordance with IFC which is an ISO standard. You can find the ifcxml file listed on this page, https://standards.buildingsmart.org/IFC/DEV/IFC4_3/RC1/HTML/link/listing-ifc4x3_rc1.htm

I would like to see an official way of nesting translations within the property templates, this would allow quite a neat version control of this serialization of the properties.